In the manufacture of electronic devices, a plasma processing apparatus is widely used for etching a workpiece. For example, the plasma processing apparatus is also used for etching a magnetic layer included in a magnetic random access memory (MRAM). In general, the plasma processing apparatus includes a processing container in which a plasma processing is performed. A stage is provided within the processing container.
The stage generally includes an electrostatic chuck and a lower electrode. The electrostatic chuck includes an electrode film surrounded by a dielectric and generates an electrostatic force when a voltage is applied to the electrode film. By this electrostatic force, the electrostatic chuck attracts and holds the workpiece. In addition, a high frequency bias for drawing ions into the workpiece is supplied to the lower electrode.
As a type of such a stage, there is a rotary stage configured to be rotatable in order to improve the uniformity of the plasma processing on a workpiece. In the rotary stage, a slip ring is used to apply a voltage to the electrode film of the electrostatic chuck and to supply a high frequency bias to the lower electrode. Such a plasma processing apparatus including a rotary stage is described in, for example, Japanese Patent Laid-Open Publication No. 01-117317.
In addition, there are two types of slip rings: a non-contact type slip ring and a contact type slip ring. In the non-contact type slip ring, as described in Japanese Patent Laid-Open Publication No. 10-143791, a medium having an electrical conductivity is filled between a stator and a rotor. For such a medium, for example, mercury is used. Further, in the contact type slip ring, a brush is provided between a stator and a rotor to electrically connect the stator and the rotor. Slip rings using a brush are described in, for example, Japanese Patent Laid-Open Publication Nos. 2009-225578 and 11-214108.